As disclosed herein the rational design of ligands provides a powerful tool to manipulate and improve transition metal catalyzed atom transfer radical polymerization (ATRP). ATRP is considered to be one of the most successful controlled radical polymerization processes with significant commercial potential for production of many specialty materials including coatings, sealants, adhesives, dispersants, materials for health and beauty products, electronics and biomedical applications. The process, including suitable transition metals and state of the art ligands, range of polymerizable monomers and materials prepared by the process, has been thoroughly described in a series of co-assigned U.S. Patents and Applications including U.S. Pat. Nos. 5,763,548; 5,807,937; 5,789,487; 5,945,491; 6,111,022; 6,121,371; 6,124,411; 6,162,882; 6,407,187; 6,512,060; 6,538,091; 6,541,580; 6,624,262; 6,624,263; 6,627,314; 6,759,491; 6,790,919; 6,887,962; 7,019,082; 7,049,373; 7,064,166; 7,125,938; 7,157,530; 7,332,550; 7,572,874; 7,678,869; 7,795,355; 7,825,199; 7,893,173; 7,893,174, 8,252,880, 8,273,823; and 8,349,410 and U.S. patent application Ser. Nos. 10/548,354; 12/311,673; 12/921,296; 12/877,589; 12/949,466; 13/026,919; 13/260504 and 13/390,470 all of which are herein incorporated by reference. These prior art patents describe the range of (co)polymerizable monomers and procedure to control the topology, architecture and ability to incorporate site specific functionality into copolymers prepared by ATRP in addition to detailing a range of composite structures that can be prepared by “grafting from” or “grafting to” a broad range of organic or inorganic materials.
ATRP has also been discussed in numerous publications with Matyjaszewski as co-author and reviewed in several book chapters: Matyjaszewski, K. et al. ACS Symp. Ser. 1998, 685, 258-283; ACS Symp. Ser. 1998, 713, 96-112; ACS Symp. Ser. 2000, 729, 270-283; ACS Symp. Ser. 2000, 765, 52-71; ACS Symp. Ser. 2000, 768, 2-26; ACS Symposium Series 2003, 854, 2-9; ACS Symp. Ser. 2009, 1023, 3-13; ACS Symp. Ser. 2012, 1100, 145-170; Chem. Rev. 2001, 101, 2921-2990; Chem Rev 2007, 107, 2270-2299 and Prog. Polym. Sci., 2007, 32, 93-146. These publications are incorporated by reference to provide additional information on the range of suitable transition metals that can participate in the redox reaction, whose generally accepted mechanism is shown in Scheme 1, and provide a prior art list of suitable ligands for the different transition metals to form transition metal complexes suitable for polymerizing a broad range of radically polymerizable (co)monomers.

Any transition metal complex (Mtn/L) capable of maintaining the dynamic equilibrium through participation in a redox reaction comprising the transferable atom or group present on each initiator or dormant polymer chain (Pn-X) to form an active radical (Pn*) and higher oxidation state transition metal complex (X-Mtn+1/L) that acts as the deactivator, may be used as the catalyst in ATRP. The creation and maintenance of a low concentration of active species, (Pn●), reduces the probability of bimolecular termination reactions, (kt), which leads to a radical polymerization process that behaves as a “living” system through retention of the stable transferable atom or group (—X) on the vast majority of growing dormant chain ends. The most frequently used ATRP procedure is based on a simple reversible halogen atom transfer catalyzed by redox active transition metal compounds, most frequently copper or iron, that form a catalyst complex with a ligand, most frequently nitrogen based ligands that modify the solubility and activity of the catalyst. The rate of the polymerization, KATRP, is defined by the ratio of activation (ka) and deactivation (kd) rate constants and the catalyst complex should be selected to favor the dormant state ensuring concurrent growth of each polymer chain and minimizing the [Pn●], Scheme 1. In this equilibrium, Pn● can deactivate by reaction with X—CuII/L, propagate with monomer (kp), or terminate (kt) with other radicals proportional to their corresponding rate constants. The ATRP equilibrium is also heavily dependent on four main reaction process variables: temperature, [Macromolecules 2009, 42, 6050-6055] pressure, [Macromol. Chem. Phys. 2011, 212, 2423-2428.] solvent, [Macromolecules 2009, 42, 6348-6360.] and selected alkyl halide/catalyst. [J. Am. Chem. Soc. 2008, 130, 10702-10713]. Of these four variables, the strongest influences reside with the polymerization solvent and catalyst, each spanning values over a range of 1×108. The procedure is a simple procedure which may be carried out in bulk, in the presence of organic solvents or in water, under homogeneous or heterogeneous conditions, in ionic liquids, and in supercritical CO2.
Early ATRP procedures employed catalyst complexes that are now recognized to be low activity [J. Am. Chem. Soc. 2008, 130, 10702-10713], and required addition of a sufficiently high concentration of the transition metal complex to overcome the effect of unavoidable increased concentration of the deactivator in the reaction medium due to radical-radical termination reactions while still driving the reaction to the desired degree of polymerization in a reasonable time frame while retaining chain end functionality. Recently novel approaches were developed that allowed regeneration of the lower oxidation state transition metal complex resulting in a significant reduction in the concentration of added catalyst. [PCT Int. Appl. WO 2005/087819] The driving force for this advance was the economic penalty associated with purification procedures, resulting from early procedures with less active catalyst complexes resulting in high concentrations of catalyst in the final product, coupled with a deeper understanding of the ATRP rate law, equation (1), which shows that Rp, the polymerization rate, depends only on the ratio of the concentration of [CuI] to [X—CuII], and does NOT depend on the absolute concentration of the copper complexes, therefore in principle, one could reduce the absolute amount of copper complex to ppm levels without affecting the polymerization rate.
                              R          p                =                                                            k                p                            ⁡                              [                M                ]                                      ⁡                          [                              P                •                            ]                                =                                                    k                p                            ⁡                              [                M                ]                                      ⁢                                                            K                  eq                                ⁡                                  [                  I                  ]                                            o                        ⁢                                          [                                  Cu                  I                                ]                                            [                                  X                  -                                      Cu                    II                                                  ]                                                                        (        1        )            
As discussed in the above incorporated references, ATRP is one of the most powerful controlled/living radical polymerization (CLRP) techniques available for the synthesis of well-defined macromolecules under versatile, industrially scalable, experimental conditions. With such a technique the synthetic polymer chemist may precisely design macromolecular architectures with predetermined molecular weights (Mn) and narrow molecular weight distributions (Mw/Mn). ATRP's utility encompasses a vast library of functional monomers, from radically copolymerizable (methyl)acrylates to styrenics and acrylamides, that can be conducted in a range of solvents (i.e. aqueous to organic), generating products with multiple potential macromolecular architectures (e.g. stars and brushes), in a range of reaction media (e.g. dispersions, emulsions, and homogenous systems).
Despite these successes, a need exists to further improve the efficiency and versatility of ATRP through optimization and development of novel catalysts [Prog. Polym. Sci. 2010, 35, 959-1021]. As described herein, the development of more active catalyst complexes may also provide an opportunity to reduce the concentration of catalyst required to drive the reaction to completion, allow one to run the reaction under milder conditions in aqueous solutions [Macromolecules 2012, 45, 6371-6379], and expand the scope of radically copolymerizable monomers to include less active monomers such as N-vinylpyrolidone, vinyl acetate and acid containing monomers such as (meth)acrylic acid. Likewise it may also expand the rage of molecules that can participate in atom transfer radical addition (ATRA) reactions and atom transfer radical coupling (ATRC) reactions [Encycl. Radicals Chem., Biol. Mater. 2012, 4, 1851-1894 sections 1.2 and 8.2].
The preparation of transition metal catalyst complexes provides a certain degree of synthetic freedom in ligand design that can manipulate and tune catalytic properties. However, as disclosed herein, the scope of designed catalyst complexes had not yet been truly exploited in ATRP. Prior to the present disclosure some of the most commonly employed and effective ligands in ATRP were tris(2-(dimethylamino)ethyl)amine (Me6TREN) [Macromolecules 1998, 31, 5958-5959] and tris(2-pyridylmethyl)amine (TPMA) [Macromolecules 1999, 32, 2434-2437], each of which are a thousand times more active than the originally used copper based catalyst complex utilizing 2,2′-bipyridine (bpy) ligands [J. Am. Chem. Soc. 1995, 117, 5614-15 and Macromolecules 1995, 28, 7901-10.].
A variety of strategies exist to manipulate catalytic activity and properties through ligand design. Indeed ligand modifications are prevalent with bpy type ligands, the class of ligands first successfully employed in copper-mediated ATRP, to provide unique properties for complexes used in asymmetric catalysis such as use of chiral 2,2′-bipyridyl ligands coordinated to Mo, Cu and Pd for allylic oxidation, [Organometallics 2001, 20, 673-690] luminescence and pH sensitivity, [Inorg. Chem. 2000, 39, 76-84] and enhanced photocatalytic activity for Ru based catalysts. [Inorg. Chem. 2012, 51, 51-62]. However, despite the vast array of modifications available to these bpy ligands, limited examples [J. Am. Chem. Soc. 2008, 130, 10702-10713] of structure-reactivity relationships exist with regard to substituents present in ligands for copper or iron based catalyst complexes suitable for an ATRP.